A conventional hand-held global positioning system (GPS) device provides positional information about the location of the GPS device by receiving and processing GPS band signals from a GPS system including satellites and base stations. Although such positional information can be quite useful, it is not convenient to carry a conventional GPS device along with a multitude of mobile wireless communications devices such as laptops, mobile phones, PDAs, or other mobile devices on which users now depend. It is therefore desirable that a GPS positioning function be included with another device, such as a wireless mobile handset.
Unfortunately, the integration of GPS technology with other mobile wireless communications devices such as, for example, cellular or personal communications services (PCS) phones has proven difficult. In particular, three alternatives have been identified for adding GPS capability to a wireless device or handset, but have proven unsatisfactory in use.
A first choice is to add GPS capability in a wireless handset by adding a separate antenna for GPS reception. Since the wireless network antenna is not modified, network communications quality is not adversely affected. However, as mobile handsets for wireless networks have become much smaller, less space is available on the handset housing to accommodate a separate, custom-designed GPS antenna. Furthermore, a GPS antenna disposed within the handset housing typically suffers from a number of reception problems. For example, poor reception can be caused by electromagnetic shielding within the handset housing and by the handset housing itself. Adjusting the electromagnetic shielding to accommodate the GPS antenna may cause substantial redesign and testing of the handset. Even the hand of the user of the wireless handset may interfere with the reception by the internal GPS antenna as the user grips the handset housing. Also, adding a separate antenna and its associated circuitry to the wireless handset adds expense and design complexity.
A second choice is to add GPS capability to a wireless handset by forcing the existing network antenna on the wireless handset to adequately receive a GPS band signal. For example, a typical dual-band antenna may be constructed to receive a PCS signal at approximately 1900 MHz and a cellular signal at approximately 800 MHz. It may therefore be possible that the existing dual-band antenna may be able to receive a GPS signal at approximately 1575 MHz. However, the GPS signal is at a non-resonant frequency for the dual-band antenna, so the received GPS signal would be less than optimal resulting in degraded signal transfer. In this regard, known dual-band antenna systems are not able to receive a GPS signal with sufficient strength and quality to implement a robust GPS location functionality on a wireless handset.
A third choice is to add GPS capability to a wireless handset by using a tri-band antenna. A tri-band antenna is constructed to receive the cellular, PCS and GPS frequencies, for example. Although such an antenna enables the GPS signal to be received, due to the limitations of antenna design such an antenna normally compromises either the cellular or PCS performance, or both. Using a tri-band antenna also substantially adds extra cost to the antenna.
Accordingly, there exists a need to add GPS position location capability in a wireless handset in a robust, economical manner. Furthermore, it would be desirable that the GPS position location capability be provided in a convenient, aesthetically pleasing manner.